LSE-68 refers to "structural metadata" provided directly from the Camera DAQ along with the pixel data. Its primary purpose is to enable the successful interpretation of the pixels in memory as an image, defining rows and columns, pre/post/over-scan, readout direction. It is now more urgent to understand the details given the likelihood of a hybrid focal plane.
There is a possibility of recording a serial number for the REB as part of this structural metadata, and that should be explored. How to link this information to the information that LSE-130 mandates about the relationship between "slot names" and physical serial numbers is an open question.